It was found that thioboronite reacted with substituted ketene (produced from α-haloacyl halide and zinc dust) and carbonyl compounds to give the corresponding α-substituted β-hydroxyalkanethioates in good yields. Also, it was established that β-hydroxyalkanoates were obtained in good yields by utilizing aluminum alkoxide in place of thioboronite in the above reaction.
Unexpected Steric Effects of “Remote” Alkyl Groups on the Rate of Conjugate Additions to Alkyl α,β-Ethylenic Sulfones, Sulfoxides, and Esters
作者:Aimee R. Usera、Gary H. Posner
DOI:10.1021/jo062155g
日期:2007.3.1
size of the heteroatom-attached alkylgroup affects the rate of conjugate addition. Molecular modeling strongly suggests that what are generally considered to be “remote” alkylgroups in −CβHCαHS(O)nalkyl systems and −CH2CβHCαHCOOalkyl systems are actually not remote from the β-carbon atom of the Michael accepting unit. Molecular modeling clearly shows that the alkylgroups in these Michael acceptors shield
在迈克尔型加成反应中对共轭乙烯砜,亚砜和酯的检测首次显示,杂原子连接的烷基的大小会影响共轭添加的速率。分子建模有力地表明,什么通常被认为是“远程”中的烷基-C β ħ Ç α HS(O)ñ烷基系统和-CH 2 C ^ β ħ Ç α HCOO烷基系统实际上是从β-不远程迈克尔接受单元的碳原子。分子模型清楚地表明,这些迈克尔受体中的烷基按以下顺序屏蔽了β-碳:Et < i -Pr < t-Bu 竞争实验确定迈克尔加成的相对比率按以下顺序排列:Et> i -Pr> t -Bu。